TY - CONF A1 - Lay, Vera A1 - Büttner, Christoph A1 - Buske, Stefan A1 - Niederleithinger, Ernst T1 - Advanced analysis of ultrasonic investigations at sealing structures N2 - Engineering barrier systems are a crucial part of the safe underground disposal of radioactive waste, particularly in salt as a host rock. Sealing structures made of tailored concrete are under test at various sites in Germany. To characterise the material properties of the concrete and potentially also the bonding to the host rock as part of the necessary subsurface structures, we apply non-destructive testing making use of advanced geophysical imaging methods. Ultrasonic investigations have been carried out at underground concrete structures in the Teutschenthal mine in Germany. Here, we show results from two distinct constructions produced in a shotcrete procedure. Our goal is to analyse the performance of ultrasonics to be used as quality assurance for sealing structures made from shotcrete. First, a ~10 m long shotcrete structure is investigated with the help of a unique Large Aperture Ultrasonic System (LAUS) allowing for depth penetration of > 9 m. We perform measurements at the front and from the side of the construction. Second, we obtain results from a 1 m thick shotcrete body containing several artificial defects (width up to 8 cm). Ultrasonic testing data were acquired using a commercial multi-static device. Additionally, a new device measuring with 3D mode instead of line mode is applied and preliminary results will be shown. Generally, the acquired ultrasonic data are analysed by the Synthetic Aperture Focusing Technique that is commonly applied in non-destructive testing. As a result, reflectors in the analysed shotcrete structures are imaged. Individual reflections from internal features and particularly the opposite wall are identified. An unexpected delamination wider than 30 cm is clearly imaged and later verified by boreholes. Thus, the method is – in general – suitable to serve as a quality measure. However, particularly the small and deep artificial defects can hardly be identified in the resulting images. Thus, we use advanced geophysical imaging methods to further enhance the quality of the obtained images. The recorded ultrasonic energy is focused to the physically reflective origin in the analysed volume. First results clearly show that we successfully improve the image quality regarding noise level and artifacts and hence facilitate the detection of objects. In total, we present a valuable experiment under realistic conditions for underground sealing structures made from shotcrete, where the locations of artificial reflectors are partly known. This experiment serves as a unique basis to analyse the performance of advanced analysis methods to obtain high-quality images of the structure’s interior. Hence, the developed ultrasonic testing and analysis schemes can serve as a part of quality assurance that will help to enable safe sealing structures for nuclear waste disposal. T2 - SafeND2023: Interdisciplinary research symposium on the safety of nuclear disposal practices CY - Berlin, Germany DA - 13.09.2023 KW - Ultrasound KW - Imaging KW - Engineered barrier systems KW - Shotcrete PY - 2023 DO - https://doi.org/10.5194/sand-2-67-2023 AN - OPUS4-58497 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rabe, U. A1 - Pudovikov, S. A1 - Herrmann, H.-G. A1 - Wiggenhauser, H. A1 - Prabhakara, Prathik A1 - Niederleithinger, Ernst T1 - Using the Corner Reflection for Depth Evaluation of Surface Breaking Cracks in Concrete by Ultrasound N2 - The corner echo is a well-known effect in ultrasonic testing, which allows detection of surface breaking cracks with predominantly perpendicular orientation to the surface as, for example, corrosion cracks in metal pipes or shafts. This echo is formed by two planes, the surface of the crack and the surface which the crack breaks. It can also be classified as a half-skip method, since a reflection of the pulse occurs on the backwall before the reflection at the defect takes place. In combination with the diffraction from the crack tip, the corner echo also allows crack sizing. As shown in this paper, the corner reflection can be used in civil engineering for nondestructive inspection of concrete. Commercially available low frequency ultrasonic arrays with dry point contact sources generate SH transversal waves with sufficient divergence of the sound field in order to detect corner reflections. Ultrasonic line-scans and area-scans were acquired with a linear array on flat concrete specimens, and the data were reconstructed by the Synthetic aperture focusing technique. If the angles and the area of reconstruction are chosen accordingly, the corner echo reflection can be distinguished from other ultrasonic information. The corner echo can thus be used as a method for deciding whether a crack is a partial-depth crack or a full-depth crack and thus for obtaining a statement about crack depth. This paper presents corresponding experimental results obtained on concrete specimens with artificial test defects and cracks induced under controlled conditions. KW - Ultrasound KW - Crack depth KW - Concrete KW - Corner echo PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-574631 DO - https://doi.org/10.1007/s10921-023-00956-8 SN - 0195-9298 VL - 42 IS - 2 SP - 1 EP - 19 PB - Springer Nature AN - OPUS4-57463 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lay, Vera A1 - Prabhakara, Prathik A1 - Mielentz, Frank A1 - Johann, Sergej A1 - Fritsch, Tobias A1 - Stamm, Michael A1 - Kühne, Hans-Carsten A1 - Niederleithinger, Ernst T1 - Material research and multi-sensory monitoring for concrete sealing structure in rock salt underground repositories N2 - Within the project SealWasteSafe, we advance construction materials and non-destructive monitoring concepts of sealing structures applied for underground disposal of nuclear waste. As these engineered barriers have high demands regarding structural integrity, an innovative alkali-activated material (AAM) that is highly suitable for the application in salt as a host rock is improved and tested on two laboratory scales. This AAM has a low heat evolution due to the reaction mechanism in comparison to common salt concretes based on Portland cement or magnesium oxychloride binders. Hence, crack formation due to thermally induced stress during the hardening process is reduced. After successful laboratory tests with small specimens (height ~5 cm), comparably manufactured large cubic (edge length 70 cm) and cylindrical specimens (height 120 cm, diameter 40 cm) are equipped with sensing technologies to demonstrate the sensors´ technical capabilities. A comprehensive multi-sensory monitoring scheme is developed and investigated to characterize and compare the different material behaviour during the setting and hardening process of two materials: (1) the newly developed AAM-based mortars with salt aggregate, and (2) a blended Portland cement-based salt concrete as reference. The analysed parameters include temperature and humidity of the material, acoustic emissions, and strain variations recorded by fiber optic cables. Passive sensor systems based on radiofrequency identification technology (RFID) embedded in the concrete provide an interface for the wireless readout of various sensors. In parallel to the embedded RFID sensors, conventional cabled systems to read out the temperature and humidity measurements are installed for comparison. Additionally, a detailed inspection of the two large cubic specimens after a monitoring period of more than six months has been undertaken. Active thermography and ultrasonic echo measurements are used to reveal potentially occurring inner cracks from the surface. To verify the non-invasive results, a core sample (diameter 2 cm) was extracted from each of the investigated cubic specimens and analysed in detail with X-ray computed tomography. Furthermore, ultrasonic methods are used for quality assurance to detect obstacles, cracks, and delamination at in-situ scale sealing structures. Experimental layout and applied imaging techniques are optimised to enhance the image quality for measurements from the front side of the engineered barrier. To characterize the inside of the test sealing structure and to improve the detection of potentially existing cracks, an ultrasonic borehole probe using the phased array technique is developed. First analyses at a half-spherical specimen coincide with modelling results and prove the reliability of the directional response caused by the phased array technique of the newly constructed ultrasonic borehole probe. Overall, the project SealWasteSafe helps to characterize construction materials and improves multi-sensory monitoring concepts and ultrasonic equipment for the sake of quality assurance. Particularly for salt as a host rock, this will help to design safe sealing structures for nuclear waste disposal. T2 - EGU General Assembly 2023 CY - Vienna, Austria DA - 23.04.2023 KW - SealWasteSafe KW - Engineered barriers KW - Salt concrete KW - Quality assurance KW - Ultrasound KW - CT KW - Thermography PY - 2023 DO - https://doi.org/10.5194/egusphere-egu23-11582 AN - OPUS4-57500 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Friedrich, Alexander A1 - Heckel, Thomas A1 - Casperson, Ralf A1 - Zhang, Tianyun A1 - Olm, G. A1 - Islam, A. A1 - Simroth, A. T1 - The AIFRI Project - Artificial Intelligence For Rail Inspection N2 - The rails of modern railways face an enormous wear and tear from ever increasing train speeds and loads. This necessitates diligent non-destructive testing for defects of the entire railway system. Non-destructive testing of rail tracks is carried out by rail inspection trains equipped with ultrasonic and eddy current test devices. However, the evaluation of the gathered data is mainly done manually with a strong focus on ultrasonic data, and defects are checked on-site using hand-held testing equipment. Maintenance measures are derived based on these on-site findings. The aim of the AIFRI project (Artificial Intelligence For Rail Inspection) is to - increase the degree of automation of the inspection process, from the evaluation of the data to the planning of maintenance measures, - increase the accuracy of defect detection, - automatically classify detected indications into risk classes. These aims will be achieved by training a neural network for defect detection and classification. Since the current testing data is unbalanced, insufficiently labeled and largely unverified we will supplement fused, simulated eddy current and ultrasonic testing data in form of a configurable digital twin. T2 - PostDoc Day 2022 CY - Berlin, Germany DA - 03.11.2022 KW - Non-destructive testing KW - Artificial intelligence KW - Simulation KW - Eddy current KW - Ultrasound PY - 2022 AN - OPUS4-57240 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Maack, Stefan A1 - Küttenbaum, Stefan A1 - Bühling, Benjamin T1 - Low-frequency ultrasound data (pulse-echo technique) with shear horizontal and longitudinal waves on the step-shaped concrete specimen “Pk050” N2 - This dataset contains raw data acquired in ultrasound measurements on a reference specimen made of concrete at Bundesanstalt für Materialforschung und -prüfung (BAM), Berlin (Germany). The internal specimen identifier is “Pk050”. The measurements were conducted using the pulse-echo method. The upper surface of the specimen was defined as measuring area. The aim of the measurements is to determine the geometrical dimensions (thickness) of the specimen “Pk050”. In addition to this, a dataset of a second specimen with identifier “Pk266” has been acquired. Pk266 has the same geometrical dimensions and concrete recipe as Pk050, but contains tendons [Reference: https://doi.org/10.7910/DVN/NUU0WZ]. KW - Ultrasound KW - Pulse echo method KW - Synthetic Aperture Focusing Technique KW - Validation KW - Elastic wave PY - 2023 DO - https://doi.org/10.7910/DVN/9EID5D PB - Harvard College CY - Cambridge, MA, USA AN - OPUS4-57231 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Maack, Stefan A1 - Küttenbaum, Stefan A1 - Bühling, Benjamin T1 - Low-frequency ultrasound data (pulse-echo technique) with shear horizontal and longitudinal waves on the step-shaped concrete specimen “Pk266” with tendons N2 - This dataset contains raw data acquired in ultrasound measurements on a reference specimen made of concrete at Bundesanstalt für Materialforschung und -prüfung (BAM), Berlin (Germany). The internal specimen identifier is “Pk266”. The measurements were conducted using the pulse-echo method. The upper surface of the specimen was defined as measuring area. The aim of the measurements is to determine both the geometrical dimensions (thickness) and the position of tendons to the measuring area. In addition to this, a second dataset of a second specimen with identifier is existing named “Pk050” has been acquired. Pk050 has the same geometrical dimensions and concrete recipe as Pk266 recipe but does not contain tendons [Reference: https://doi.org/10.7910/DVN/9EID5D]. KW - Ultrasound KW - Pulse echo method KW - Synthetic Aperture Focusing Technique KW - Validation KW - Elastic wave PY - 2023 DO - https://doi.org/10.7910/DVN/NUU0WZ PB - Harvard College CY - Cambridge, MA, USA AN - OPUS4-57232 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lay, Vera A1 - Effner, Ute A1 - Niederleithinger, Ernst A1 - Arendt, J. A1 - Kudla, W. T1 - Ultrasonic quality assurance for underground salt shotcrete sealing structures in Teutschenthal mine, Germany N2 - Underground sealing structures are necessary to seal radioactive or toxic waste in underground repositories. A special version of MgO concrete is used in the mine in Teutschenthal and applied at a large-scale test with the aim to provide a low permeability barrier. The test structures (up to 10 m long) were created by shotcreting. Besides destructive tests, non-destructive ultrasonic measurements have been evaluated for quality assurance to monitor potential anomalies such as cracks, concrete inhomogeneities, and delamination. We show results of ultrasonic measurements with a multi-transducer system used at the front and from the side of the concrete structure. Images are obtained by synthetic aperture focusing techniques. The boundaries between concreting sections are not visible in the ultrasonic images systematically so that a successful concreting is assumed, which is confirmed by the low permeabilities observed. Several reflectors up to a depth of 1.2 m are identified and interpreted as potential damages in the concrete. Phase analysis of prominent reflectors reveal a negative impedance contrast thus indicating air filled voids, cracks or delamination. Boreholes through some of the identified reflectors are used to verify the results from ultrasonic measurements. Additionally, an experiment with incorporated artificial defects was undertaken to analyse the reliability of the applied methods. Overall, the conducted tests show the potential of ultrasonic measurements to detect critical anomalies. Despite challenges at small-scale structures (cm-order), large-scale anomalies can be identified. Consequently, implementing ultrasonic monitoring during and after the construction of concrete sealing structures has shown its potential as a tool for quality assurance, but needs further development and validation. T2 - NDT-CE 2022 CY - Zurich, Switzerland DA - 16.08.2022 KW - Ultrasound KW - Ultrasonic imaging KW - Magnesia shotcrete KW - Underground KW - Engineered barrier systems PY - 2022 UR - https://www.ndt.net/events/proceedings/topic.php?eventID=292&TopicID=27209 SP - 1 EP - 4 PB - NDT.net AN - OPUS4-55824 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lay, Vera A1 - Effner, Ute A1 - Niederleithinger, Ernst A1 - Arendt, J. A1 - Kudla, W. T1 - Ultrasonic quality assurance for underground salt shotcrete sealing structures in Teutschenthal mine, Germany N2 - Underground sealing structures are necessary to seal radioactive or toxic waste in underground repositories. Particularly developed MgO concrete is used in the mine in Teutschenthal and applied at a large-scale test with the aim to provide concrete with low permeabilities. The test structures (up to 10 m long) were created with the help of a shotcrete procedure. Besides destructive tests, non-destructive ultrasonic measurements are used for quality assurance to monitor potential anomalies such as cracks, concrete inhomogeneities, and delamination. We show results of ultrasonic measurements with a multi-transducer system used at the front site of the concrete structure. Images are obtained by synthetic aperture focusing techniques. Concreting sections are not systematically imaged so that a successful concreting is assumed as also indicated by observed low permeabilities. Several reflectors up to a depth of 1.2 m are identified and interpreted as potential damages in the concrete. Phase analysis of prominent reflectors reveal a negative impedance contrast thus indicating air filled voids, cracks or delamination. Boreholes through some of the identified reflectors are used to verify the results from ultrasonic measurements. Additionally, an experiment with incorporated defects is undertaken to analyse the reliability of the applied methods. Overall, the conducted tests show the great potential of ultrasonic measurements to detect critical anomalies. Despite challenges at small-scale structures (cm-order), large-scale anomalies can be identified. Implementing ultrasonic monitoring during and after the construction of concrete sealing structures is recommended as a tool for quality assurance. T2 - NDT-CE 2022 CY - Zurich, Switzerland DA - 16.08.2022 KW - Ultrasound KW - Ultrasonic imaging KW - Magnesia shotcrete KW - Underground KW - Engineered barrier systems PY - 2022 AN - OPUS4-55825 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Memmolo, V. A1 - Lugovtsova, Yevgeniya A1 - Olino, M. A1 - Prager, Jens ED - Kundu, T. ED - Reis, H. ED - Ihn, J.-B. T1 - Application of Temperature Compensation Strategies for Ultrasonic Guided Waves to Distributed Sensor Networks N2 - Temperature compensation strategies play a key role in the implementation of guided wave based structural health monitoring approaches. The varying temperature influences the performance of the inspection system inducing false alarms or missed detection, with a consequent reduction of reliability. This paper quantitatively assesses two temperature compensation methods, namely the optimal baseline selection (OBS) and the baseline signal stretch (BSS), with the aim to extend their use to the case of distributed sensor networks (DSN). The effect of temperature separation between baseline time-traces in OBS and BSS are investigated considering multiple couples of sensors employed in the DSN. A decision strategy that uses frequent value warning to define the optimal baseline or stretching parameter is found to be effective analyzing data from two several experiments, which use different frequency analysis with either predominantly A0 mode or S0 mode data or both. The focus is given on the fact that different paths are available in a sensor network and several possible combinations of results are available. Nonetheless, introducing a frequent value warning it is possible to increase the efficiency of the OBS and BSS approach making use of fewer signal processing algorithms. In addition, the effectiveness of those approach is quantified using damage indicators as metric, which confirms that the performance of OBS and BSS quantitatively agree with predictions and also demonstrate that the use of compensation strategies improve detectability of damage with a higher reliability of the system. T2 - 2022 49th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE 2022) CY - San Diego, CA, USA DA - 25.07.2022 KW - Ultrasound KW - Elastic waves KW - Structural Health Monitoring KW - Environmental Effects KW - Damage Detection PY - 2022 SN - 978-0-7918-8659-5 DO - https://doi.org/10.1115/QNDE2022-98534 SP - 1 PB - The American Society of Mechanical Engineers (ASME) CY - 2 Park Avenue, New York, NY 10016, USA AN - OPUS4-57074 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Bühling, Benjamin T1 - Acoustic and flow data of an ultrasonic fluidic switch and an ultrasonic piezoelectric transducer N2 - This dataset contains acoustic and flow data of an ultrasonic fluidic switch, which have been acquired using a microphone, a hot-wire anemometer and a pitot tube. Furthermore, acoustic data of a commercial piezoelectric transducer is provided. KW - Fluidics KW - Air-coupled ultrasound KW - Ultrasound KW - Non-destructive testing KW - Acoustic-flow interaction KW - Piezoelectric transducer PY - 2020 DO - https://doi.org/10.7910/DVN/OQYPC9 PB - Harvard College CY - Cambridge, MA, USA AN - OPUS4-52392 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Niederleithinger, Ernst T1 - Advances in ultrasonic testing and monitoring of concrete structures N2 - Recent years have seen extended use of ultrasonic techniques for concrete infrastructure assessement. They are applied for quality assurance and condition assessement at bridges, power plants, dams and other important objects. However, there are still a couple of significant limitations. They include, but are not limited to depth of penetration, imaging complex structures or early stage detections of distributed damage. The talk will give information on recent research in this area. Specifically, the application of the unique deep penetration system LAUS is shown. Ultrasonic monitoring using embedded transducers to check for subtle and sudden changes in the material is introduced as well. Comments on initiatives for validation, standardization and certification will be given. T2 - 341e Conférence CERES CY - Online meeting DA - 26.10.2020 KW - Concrete KW - Ultrasound KW - Imaging KW - Monitoring PY - 2020 AN - OPUS4-51463 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bühling, Benjamin A1 - Maack, Stefan A1 - Strangfeld, Christoph T1 - OsciCheck - Fluidic Generation of Ultrasound N2 - The OsciCheck project is presented. The working principle and sound field of a fluidic switch is described. Future goals of the project are presented. T2 - CoDA Summer School 2020 CY - Berchtesgaden, Germany DA - 28.09.2020 KW - Fluidic Switch KW - Air-coupled ultrasound KW - Ultrasound KW - Non-destructive testing KW - Fluidischer Schalter KW - Luftgekoppelter Ultraschall KW - Ultraschall KW - Zerstörungsfreie Prüfung PY - 2020 AN - OPUS4-51380 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Epple, Niklas A1 - Fontoura Barroso, Daniel A1 - Niederleithinger, Ernst T1 - Monitoring of Concrete with Embedded Ultrasound Sensors, Coda Waves and a Novel Measurement Device N2 - Using embedded ultrasound (US) sensors in civil engineering structures and Coda Wave Interferometry (CWI), DFG research group CoDA aims for developing methods of concrete damage assessment by combination of Micro and macro scale simulations and experiments. BAMs goal within the project is the provision of small and durable measurement equipment on the one hand, and the investigation of damage sensitive parameters and development of an imaging algorithm on the other hand. In this study we focus on the development of the measurement system and the influence of temperature variations on the measurements. T2 - Summer School DFG FOR CoDA CY - Berchtesgaden, Germany DA - 27.09.2020 KW - Ultrasound KW - Coda Wave Interferometry KW - Structural Health Monitoring PY - 2020 AN - OPUS4-51382 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Strangfeld, Christoph A1 - Bühling, Benjamin A1 - Maack, Stefan T1 - Adaption of fluidic devices for SHM of hydrogen tanks N2 - Frequency analysis of the tank during every filling Passive actuator is integrated inside filling nozzle/ pressure vessel Frequency from 5 kHz to 150 kHz Frequency sweep (Chirp) can be performed Works with every fluid: air, hydrogen, oxygen, argon, water. T2 - H2Safety Kompetenzzentrum CY - BAM Berlin, Germany DA - 07.07.2021 KW - Fluidic device KW - Structural health monitoring KW - Hydrogen tank KW - Ultrasound PY - 2021 AN - OPUS4-52930 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wang, Xin A1 - Niederleithinger, Ernst A1 - Hindersmann, Iris T1 - The installation of embedded ultrasonic transducers inside a bridge to monitor temperature and load influence using coda wave interferometry technique N2 - This article presents a unique method of installing a special type of embedded ultrasonic transducers inside a 36-m-long section of an old bridge in Germany. A small-scale load test was carried out by a 16 ton truck to study the temperature and load influence on the bridge, as well as the performance of the embedded transducers. Ultrasonic coda wave interferometry technique, which has high sensitivity in detecting subtle changes in a heterogeneous medium, was used for the data evaluation and interpretation. The separation of two main influence factors (load effect and temperature variation) is studied, and future applications of wave velocity variation rate Φ for structural health condition estimation are discussed. As a preliminary research stage, the installation method and the performance of the ultrasonic transducer are recognized. Load- and temperature-induced weak wave velocity variations are successfully detected with a high resolution of 10−4%. The feasibility of the whole system for long-term structural health monitoring is considered, and further research is planned. KW - Ultrasound KW - Bridge KW - Monitoring KW - coda wave interferometry KW - embedded PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-527978 DO - https://doi.org/10.1177/14759217211014430 SN - 1475-9217 VL - 21 IS - 3 SP - 913 EP - 927 PB - SAGE AN - OPUS4-52797 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zeipert, H. A1 - Claes, L. A1 - Johannesmann, S. A1 - Webersen, M. A1 - Lugovtsova, Yevgeniya A1 - Prager, Jens A1 - Henning, B. T1 - Measurement and simulation of Lamb waves in adhesive-bonded multilayer systems N2 - Lamb waves are a common tool in the field of non-destructive testing and are widely used for material characterisation. Further, the increasing computational capability of modern systems enables the Simulation of complex and detailed material models. This work demonstrates the possibility of simulating an adhesive-bonded multilayer system by characterising each layer individually, and introduces an Approach for determining the dispersive behaviour of acoustic waves in a multilayer system via real measurements. T2 - SMSI 2021 Conference – Sensor and Measurement Science International CY - Online meeting DA - 03.05.2021 KW - Adhesive bonds KW - Lamb waves KW - Elastic constants KW - Non-Destructive Testing KW - Ultrasound PY - 2021 AN - OPUS4-52635 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zeipert, H. A1 - Claes, L. A1 - Johannesmann, S. A1 - Webersen, M. A1 - Lugovtsova, Yevgeniya A1 - Prager, Jens A1 - Henning, B. T1 - Measurement and simulation of Lamb waves in adhesive-bonded multilayer systems N2 - Lamb waves are a common tool in the field of non-destructive testing and are widely used for materialcharacterisation. Further, the increasing computational capability of modern systems enables the Simulation of complex and detailed material models. This work demonstrates the possibility of simulating an adhesive-bonded multilayer system by characterising each layer individually, and introduces an Approach for determining the dispersive behaviour of acoustic waves in a multilayer system via real measurements. T2 - SMSI 2021 Conference – Sensor and Measurement Science International CY - Online meeting DA - 03.05.2021 KW - Adhesive bonds KW - Lamb waves KW - Elastic constants KW - Non-Destructive Testing KW - Ultrasound PY - 2021 DO - https://doi.org/10.5162/SMSI2021/A8.2 SP - 91 EP - 92 AN - OPUS4-52634 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schweitzer, T. A1 - Hörmann, M. A1 - Bühling, Benjamin A1 - Bobusch, B. T1 - Switching Action of a Bistable Fluidic Amplifier for Ultrasonic Testing N2 - Air-coupled ultrasonic testing is widely used in the industry for the non-destructive testing of compound materials. It provides a fast and efficient way to inspect large concrete civil infrastructures for damage that might lead to catastrophic failure. Due to the large penetration depths required for concrete structures, the use of traditional piezoelectric transducer requires high power electric systems. In this study, a novel fluidic transducer based on a bistable fluidic amplifier is investigated. Previous experiments have shown that the switching action of the device produces a high-power broadband ultrasonic signal. This study will provide further insight into the switching behaviour of the fluidic switch. Therefore, parametric CFD simulations based on compressible supersonic RANS simulations were performed, varying the inlet pressure and velocity profiles for the control flow. Switching times are analyzed with different methods, and it was found that These are mostly independent of the slope of the velocity profile at the control port. Furthermore, it was found that an inversely proportional relationship exists between flow velocity in the throat and the switching time. The results agree with the theoretical background established by experimental studies that can be found in the literature. KW - Ultrasound KW - Non-destructive testing KW - Fluidic devices KW - Computational fluid dynamics KW - Concrete KW - Bistable fluidic amplifier PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-525115 DO - https://doi.org/10.3390/fluids6050171 SN - 2311-5521 VL - 6 IS - 5 SP - 171 PB - MDPI CY - Basel, Switzerland AN - OPUS4-52511 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Olino, M. A1 - Lugovtsova, Yevgeniya A1 - Memmolo, V. A1 - Prager, Jens T1 - Temperature Compensation Strategies for Lamb Wave Inspection using Distributed Sensor Networks N2 - The application of temperature compensation strategies is crucial in structural health monitoring approaches based on guided waves. Actually, the varying temperature influences the performance of the inspection system inducing false alarms or missed detection, with a consequent reduction of reliability. This paper quantitatively describes a method to compensate the temperature effect, namely the optimal baseline selection (OBS), extending its application to the case of distributed sensor networks (DSN). The effect of temperature separation between baseline time-traces in OBS are investigated considering multiple couples of sensors employed in the DSN. A combined strategy that uses both OBS and frequent value warning is considered. Theoretical results are compared, using data from two several experiments, which use different frequency analysis with either predominantly A0 mode or S0 mode data or both. The focus is given on the fact that different paths are available in a sensor network and several possible combination of results are available. Nonetheless, introducing a frequent value warning it is possible to increase the efficiency of the OBS approach making use of fewer signal processing algorithms. These confirm that the performance of OBS quantitatively agrees with predictions and also demonstrate that the use of compensation strategies improve detectability of damage. T2 - IEEE International Workshop on Metrology for AeroSpace CY - Pisa, Italy DA - 27.06.2022 KW - Ultrasound KW - Ultrasonic Guided Waves KW - Structural Health Monitoring PY - 2022 SN - 978-1-6654-1076-2 DO - https://doi.org/10.1109/MetroAeroSpace54187.2022.9856029 SP - 598 EP - 601 AN - OPUS4-55268 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Niederleithinger, Ernst T1 - Introduction to BAM and ultrasonics (and GPR) in civil engineering N2 - This presentation gives anoverview about BAM, its department 8 and in particular its division 8.2 "NDT methods for civil engineering". The focus is on methods and applications with a geoscientific context, such as methods adopted from geophysics or NDT method applied in a geological environment. T2 - GTK (Geological Survey of Finland) Semninar CY - Espoo, Finland DA - 20.01.2023 KW - NDT KW - Ultrasound KW - Radar KW - Geophysics KW - Concrete PY - 2023 AN - OPUS4-56911 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tiitta, M. A1 - Tiitta, V. A1 - Gaal, Mate A1 - Heikkinen, J. A1 - Lappalainen, R. A1 - Tomppo, L. T1 - Air-coupled ultrasound detection of natural defects in wood using ferroelectret and piezoelectric sensors N2 - Air-coupled ultrasound was used for assessing natural defects in wood boards by through-transmission scanning measurements. Gas matrix piezoelectric (GMP) and ferroelectret (FE) transducers were studied. The study also included tests with additional bias voltage with the ferroelectret receivers. Signal analyses, analyses of the measurement dynamics and statistical analyses of the signal parameters were conducted. After the measurement series, the samples were cut from the measurement regions and the defects were analyzed visually from the cross sections. The ultrasound responses were compared with the results of the visual examination of the cross sections. With the additional bias voltage, the ferroelectret measurement showed increased signal-to-noise ratio, which is especially important for air-coupled measurement of high-attenuation materials like wood. When comparing the defect response of GMP and FE sensors, it was found that FE sensors had more sensitive dynamic range, resulting from better s/n ratio and short response pulse. Classification test was made to test the possibility of detecting defects in sound wood. Machine learning methods including decision trees, k-nearest neighbor and support vector machine were used. The classification accuracy varied between 72 and 77% in the tests. All the tested machine learning methods could be used efficiently for the classification. KW - Air-coupled transducers KW - Wood KW - Ultrasound KW - Ultrasonic imaging KW - Ferroelectret KW - Machine learning PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-509503 DO - https://doi.org/10.1007/s00226-020-01189-y SP - 1 EP - 14 PB - Springer AN - OPUS4-50950 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Vössing, Konrad A1 - Gaal, Mate A1 - Niederleithinger, Ernst T1 - Imaging wood defects using air coupled ferroelectret ultrasonic transducers in reflection mode N2 - Air-coupled ultrasound (ACU) is used to detect defects in wood panels without physically contacting the sample and with a quick scanning rate. Transducers made of cellular polypropylene (PP) with a high signal-to-noise ratio are quite suitable for ACU testing of wood. The extremely low modulus of elasticity and low density of PP transducers results in a small difference in acoustic impedance for the Transmission of ultrasonic waves between the transducer and air, allowing new areas of application to become possible. To demonstrate the suitability of the reflection technique, measurements are shown on the three samples Multiplex, LVL, and MDF and compared with transmission measurements. Due to this acoustic barrier and the use of cellular PP transducers, an exact detection of delamination and cavities is possible in wood panels up to 40 mm thick. If only one side of an object is accessible and the depth of the defect is of interest, the reflection technique is preferred at the expense of a reduced measuring accuracy and Penetration depth. KW - Wood KW - Ultrasound KW - Air coupled KW - Defects PY - 2020 DO - https://doi.org/10.1016/j.conbuildmat.2020.118032 VL - 241 SP - 118032, 1 EP - 8 PB - Elsevier Ltd. AN - OPUS4-50235 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Niederleithinger, Ernst T1 - Ultrasonic methods for concrete: To boldly see, what we have not seen before N2 - This keynote talk at NDE 2019 discusses specific progress in ultrasonic testing of concrete structures. A deep penetration instrument (LAUS) is introduced as well as advanced imaging methods adopted from geophysics and new approaches to ultrasonic monitoring. T2 - NDE 2019 CY - Bangalore, India DA - 05.12.2019 KW - NDT KW - Concrete KW - Ultrasound KW - Imaging KW - Monitoring PY - 2019 AN - OPUS4-50170 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Heckel, Thomas A1 - Wack, Y. A1 - Mook, G. T1 - Simulation of an instrumented ultrasonic test run with a rail inspection train N2 - Rail inspection performed by ultrasonic rail inspection trains is a complex and challenging process. A large number of variables and parameters given by the environment, the track and the testing-system have an influence on the overall performance of the inspection and the inspection result. Typically the parameter vary in a combination depending on the track condition. To evaluate the individual influence of each relevant variable, simulation tools can be used. Therefore the entire inspection process has to be transferred into a model using combined modelling techniques. The goal of this work is to model an instrumented ultrasonic test run with a rail inspection train with the parameters varied by a script over a virtually driven distance. T2 - 46th Annual Review of Progress in Quantitative Nondestructive Evaluation- QNDE 2019 CY - Portland, OR, USA DA - 14.07.2019 KW - Ultrasound KW - Rail inspection KW - Modelling KW - Simulation PY - 2019 VL - 2019 SP - 1 EP - 3 AN - OPUS4-49839 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Clauß, F. A1 - Epple, Niklas A1 - Ahrens, M. A. A1 - Niederleithinger, Ernst A1 - Mark, P. T1 - Correlation of Load-Bearing Behavior of Reinforced Concrete Members and Velocity Changes of Coda Waves N2 - The integral collection of information such as strains, cracks, or temperatures by ultrasound offers the best prerequisites to monitor structures during their lifetime. In this paper, a novel approach is proposed which uses the collected information in the coda of ultrasonic signals to infer the condition of a structure. This approach is derived from component tests on a reinforced concrete beam subjected to four-point bending in the lab at Ruhr University Bochum. In addition to ultrasonic measurements, strain of the reinforcement is measured with fiber optic sensors. Approached by the methods of moment-curvature relations, the steel strains serve as a reference for velocity changes of the coda waves. In particular, a correlation between the relative velocity change and the average steel strain in the reinforcement is derived that covers 90% of the total bearing capacity. The purely empirical model yields a linear function with a high level of accuracy (R 2 =0.99, R2=0.99, RMSE≈90μ RMSE≈90μ strain). KW - Ultrasound KW - Coda Wave Interferometry (CWI) KW - Structural Health Monitoring KW - Reinforced Concrete KW - Embedded Sensors PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-542316 DO - https://doi.org/10.3390/ma15030738 VL - 15 IS - 3 SP - 738 PB - MDPI AN - OPUS4-54231 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chakraborty, J. A1 - Wang, Xin A1 - Stolinski, M. T1 - Analysis of Sensitivity of Distance between Embedded Ultrasonic Sensors and Signal Processing on Damage Detectability in Concrete Structures N2 - Damage detection of reinforced concrete (RC) structures is becoming a more attractive domain due to the safety issues arising in the last few decades. The damage in concrete can be caused by excessive exploitation of the structure or environmental effects. The cracks in concrete can be detected by different nondestructive testing methods. However, the available methods used for this purpose have numerous limitations. The technologies available in the market nowadays have difficulties detecting slowly progressive, locally limited damage. In addition, some of These methods cannot be applied, especially in hard-to-reach areas in the superstructures. In order to avoid these deficiencies, an embedded ultrasonic methodology can be used to detect cracks in RC structures. In this study, the methodology of crack detection supported with the advanced Signal processing algorithm was proposed and verified on RC structures of various types, and cracks occurring between embedded sensors can be detected. Moreover, different pairs of ultrasonic sensors located in the considered structures are used for the analysis of the sensitivity of distance between them. It is shown that the ultrasonic sensors placed in the range of 1.5–2 m can detect cracks, even when the other methods failed to detect changes in the structure. The obtained results confirmed that diffuse ultrasonic sensor methodology is able to monitor real structures more effectively than traditional techniques. KW - Ultrasound KW - Coda wave interferometry KW - Structural health monitoring PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-543624 DO - https://doi.org/10.3390/acoustics4010007 VL - 4 IS - 1 SP - 89 EP - 110 PB - MDPI CY - Basel, Schweiz AN - OPUS4-54362 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kruschwitz, Sabine A1 - Oesch, T. A1 - Mielentz, Frank A1 - Meinel, Dietmar A1 - Spyridis, P. T1 - Non-Destructive Multi-Method Assessment of Steel Fiber Orientation in Concrete N2 - Integration of fiber reinforcement in high-performance cementitious materials has become widely applied in many fields of construction. One of the most investigated advantages of steel Fiber reinforced concrete (SFRC) is the deceleration of crack growth and hence its improved sustainability. Additional benefits are associated with its structural properties, as fibers can significantly increase the ductility and the tensile strength of concrete. In some applications it is even possible to entirely replace the conventional reinforcement, leading to significant logistical and environmental benefits. Fiber reinforcement can, however, have critical disadvantages and even hinder the Performance of concrete, since it can induce an anisotropic material behavior of the mixture if the fibers are not appropriately oriented. For a safe use of SFRC in the future, reliable non-destructive testing (NDT) methods need to be identified to assess the fibers’ orientation in hardened concrete. In this study, ultrasonic material testing, electrical impedance testing, and X-ray computed tomography have been investigated for this purpose using specially produced samples with biased or random Fiber orientations. We demonstrate the capabilities of each of these NDT techniques for fiber orientation measurements and draw conclusions based on these results about the most promising areas for future research and development. KW - Spectral induced polarization KW - Steel fiber reiniforced concrete KW - Fiber orientation KW - Non-destructive testing KW - Micro-computed tomography KW - Ultrasound PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-543520 DO - https://doi.org/10.3390/app12020697 VL - 12 IS - 2 SP - 1 EP - 14 PB - MDPI CY - Basel Switzerland AN - OPUS4-54352 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Epple, Niklas A1 - Fontoura Barroso, Daniel A1 - Hau, Julia A1 - Niederleithinger, Ernst ED - Cunha, A. ED - Caetano, E. T1 - Accounting for Long Term Environmental Influences on Ultrasonic Monitoring Measurements of Reinforced Concrete Constructions with Embedded Transducers N2 - Ultrasound measurements in concrete are a well-known technique in civil engineering and non-destructive testing. For consistent monitoring of a concrete structure, the common techniques, using external sensors can often not provide the appropriate degree of repeatability, as the surface of structures changes, and comparable coupling conditions cannot be guaranteed when a measurement is repeated after some time. By embedding ultrasound transducers in concrete, we aim to develop a strategy for long-term monitoring of infrastructure, especially bridges, as a supplement and extension to other techniques. Applying the so-called coda wave interferometry to these measurements we can detect subtle changes in the medium far beyond the Resolution limit of traditional time of flight methods. A smart sensor layout enables cost-efficient sensing of the entire area of interest. Embedding the transducers might remove uncertainties like coupling or positioning changes, while other challenges remain. Temperature and moisture content influence the structure and the transducers. These drifts need to be recorded and removed and good coupling must be ensured while not being able to visually inspect the sensor. In a multidisciplinary research group funded by the German Research Foundation, we aim to solve these problems on the way towards an ultrasound monitoring system for reinforced concrete structures. In various experiments in the lab and field, we determine the influence of temperature variations on the measurements and the equipment. As the monitoring task is the detection of irreversible damages - not reversible changes - a smart system requires a smart way of discrimination between permanent damages and reversible changes. With the data collected in these experiments, we present an approach to an environmental correction to ultrasound data to avoid a misinterpretation of these environmental changes as damage indicators. T2 - 10th International Conference on Structural Health Monitoring of Intelligent Infrastructure CY - Porto, Portugal DA - 30.06.2021 KW - Ultrasound KW - Coda Wave Interferometry (CWI) KW - Structural Health Monitoring KW - Embedded Sensors PY - 2021 SP - 1 EP - 7 AN - OPUS4-54007 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Epple, Niklas A1 - Niederleithinger, Ernst A1 - Barroso, Daniel A1 - Lange, Marco A1 - Wöstmann, Jens T1 - Bridge Monitoring with Coda Waves - Embedding Ultrasonic Transducers in a Reinforced Concrete Bridge to Monitor Small Changes in Multiply Scattered Waves N2 - Within a DFG-funded research group, we investigate the possibility of concrete damage assessment with coda waves. Coda wave interferometry (CWI) can be a valuable asset to structural health monitoring (SHM) as we can detect small signal changes and quantify them with the calculation of relative velocity changes. By equipping an in-service road bridge with more than 24 embedded ultrasonic transducers, we want to analyze how methods developed within the research group perform in an uncontrollable environment. We evaluate individual source-receiver combinations for detection of temporal changes as well as the entire installed sensor array to create maps of material change comparing two distinct states of the bridge. T2 - Research Unit CoDA Summer School 2 CY - Garmisch-Partenkirchen, Germany DA - 19.07.2022 KW - Coda Wave Interferometry KW - Embedded sensors KW - Structural Health Monitoring KW - Ultrasound KW - Reinforced Concrete Structures PY - 2022 AN - OPUS4-55382 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Epple, Niklas A1 - Fontoura Barroso, Daniel A1 - Niederleithinger, Ernst A1 - Hindersmann, I. A1 - Sodeikat, C. A1 - Groschup, R. T1 - Monitoring of a German Road Bridge Using Embedded Ultrasonic Transducers and Coda Waves N2 - The ‘G¨anstorbr¨ucke’ bridge between the cities of Ulm and Neu-Ulm is one of the best-monitored bridges all over Germany. In addition to an already active bride monitoring system, we have equipped the bridge with 30 ultrasonic transducers to explore the monitoring possibilities at an in-service large-scale reinforced concrete structure with continuous active ultrasonic measurements. The monitoring system is based on the detection of small changes in the entire signal, especially the multiply scattered parts of the recording, the so-called coda. Applying Coda Wave Interferometry (CWI), subtle changes in the signal can be detected and related to changing velocities in the area between source and receiver. A comparison of the results from coda wave interferometry with the strain measurements of the permanent monitoring system shows a correlation between strain measurements and CWI results. We discuss the challenges of changing environmental conditions, pose for interpretation of the results, and highlight the advantages of embedded versus externally attached ultrasonic transducers in permanent bridge monitoring, especially when coda wave interferometry is applied. T2 - EWSHM 2022 CY - Palermo, Italy DA - 04.07.2022 KW - Bridge monitoring KW - Ultrasound KW - Embedded sensors KW - Coda wave interferometry PY - 2022 AN - OPUS4-55383 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Epple, Niklas A1 - Fontoura Barroso, Daniel A1 - Niederleithinger, Ernst A1 - Hindersmann, I. A1 - Sodeikat, C. A1 - Groschup, R. ED - Rizzo, P. ED - Milazzo, A. T1 - From the Lab to the Structure: Monitoring of a German Road Bridge Using Embedded Ultrasonic Transducers and Coda Waves N2 - The ‘Gänstorbrücke’ bridge between the cities of Ulm and Neu-Ulm is one of the best-monitored bridges all over Germany. In addition to an already active bride monitoring system, we have equipped the bridge with 30 ultrasonic transducers to explore the monitoring possibilities at an in-service large-scale reinforced concrete structure with continuous active ultrasonic measurements. The monitoring system is based on the detection of small changes in the entire signal, especially the multiply scattered parts of the recording, the so-called coda. Applying Coda Wave Interferometry (CWI), subtle changes in the signal can be detected and related to changing velocities in the area between source and receiver. A comparison of the results from coda wave interferometry with the strain measurements of the permanent monitoring system shows a correlation between strain measurements and CWI results. We discuss the challenges of changing environmental conditions, pose for interpretation of the results, and highlight the advantages of embedded versus externally attached ultrasonic transducers in permanent bridge monitoring, especially when coda wave interferometry is applied. KW - Bridge monitoring KW - Ultrasound KW - Embedded sensors KW - Coda wave interferometry PY - 2022 SN - 978-3-031-07258-1 DO - https://doi.org/10.1007/978-3-031-07258-1_83 VL - 254 SP - 824 EP - 832 PB - Springer Cham CY - Cham AN - OPUS4-55385 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bruno, Giovanni T1 - Micro Non-Destructive Testing and Evaluation N2 - What is meant by ‘Micro Non-Destructive Testing and Evaluation’? This was the central subject of debate in this Special Issue. At present, sub-millimeter-size components or even assemblies are pervading the industrial and scientific world. Classic examples are electronic devices and watches (as well as parts thereof), but recent examples encompass additively manufactured lattice structures, stents, or other microparts. Moreover, most assemblies contain micro-components. Testing such components or their miniaturized parts would fit well within the topic of micro non-destructive testing and evaluation. In all cases, performance and integrity testing, quality control, and dimensional tolerances need to be measured at the sub-millimeter level (ideally with a spatial resolution of about a micron); most of the time, such features and components are embedded in much larger assemblies, which also need to be taken into account. The solution to this dilemma (i.e. measuring large parts with high resolution) depends on the part and on the problem under consideration. Another possible definition of micro non-destructive testing and evaluation can relate to the characterization of micro-features (e.g., the microstructure) in much larger specimens, such as damage in concrete cores or porosity in additively manufactured components. A further aspect is the use of microscopic probes to evaluate macroscopic properties. This is the case, for instance but not at all exclusively, in the use of diffraction techniques to determine macroscopic stress. The splits between testing and characterization at the micro-level (or of micro parts) from one side and handling of macroscopic assemblies on the other represent a great challenge for many fields of materials characterization. On top of that, including the use of microscopic methods to test integrity would add a further level of complexity. Imaging, mechanical testing, non-destructive testing, measurement of properties, structural health monitoring, and dimensional metrology all need to be re-defined if we want to cope with the multi-faceted topic of micro non-destructive testing and evaluation. The challenge has already been accepted by the scientific and engineering communities for a while but is still far from being universally tackled. This Special Issue yields an interesting answer to the questions posed above. It presents the progress made and the different aspects of the challenge as well as at indicates the paths for the future of NDT&E. KW - Ultrasound KW - Materials Characterization KW - Residual Stress KW - Thermography Computed KW - Tomography KW - Non-destructive Testing KW - Magnetic Methods PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-556849 DO - https://doi.org/10.3390/ma15175923 VL - 15 IS - 17 SP - 1 EP - 3 PB - MDPI CY - Basel, Schweiz AN - OPUS4-55684 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Diewald, F. A1 - Epple, Niklas A1 - Kraenkel, T. A1 - Gehlen, C. A1 - Niederleithinger, Ernst T1 - Impact of External Mechanical Loads on Coda Waves in Concrete N2 - During their life span, concrete structures interact with many kinds of external mechanical loads. Most of these loads are considered in advance and result in reversible deformations. Nevertheless, some of the loads cause irreversible, sometimes unnoticed changes below the macroscopic scale depending on the type and dimension of the impact. As the functionality of concrete structures is often relevant to safety and society, their condition must be known and, therefore, assessed on a regular basis. Out of the spectrum of non-destructive monitoring methods, Coda Wave Interferometry using embedded ultrasonic sensors is one particularly sensitive technique to evaluate changes to heterogeneous media. However, there are various influences on Coda waves in concrete, and the interpretation of their superimposed effect is ambiguous. In this study, we quantify the relations of uniaxial compression and uniaxial tension on Coda waves propagating in normal concrete. We found that both the signal correlation of ultrasonic signals as well as their velocity variation directly reflect the stress change in concrete structures in a laboratory environment. For the linear elastic range up to 30% of the strength, we calculated a velocity variation of −0.97‰/MPa for compression and 0.33%/MPa for tension using linear regression. In addition, these parameters revealed even weak irreversible changes after removal of the load. Furthermore, we show the time-dependent effects of shrinkage and creep on Coda waves by providing the development of the signal parameters over time during half a year together with creep recovery. Our observations showed that time-dependent material changes must be taken into account for any comparison of ultrasonic signals that are far apart in time. The study’s results demonstrate how Coda Wave Interferometry is capable of monitoring stress changes and detecting even small-size microstructural changes. By indicating the stated relations and their separation from further impacts, e.g., temperature and moisture, we anticipate our study to contribute to the qualification of Coda Wave Interferometry for its application as an early-warning system for concrete structures. KW - Ultrasound KW - Coda Wave Interferometry (CWI) KW - Mechanical Load KW - Microstructure KW - Concrete PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-556878 DO - https://doi.org/10.3390/ma15165482 SN - 1996-1944 VL - 15 IS - 16 SP - 1 EP - 15 PB - MDPI AN - OPUS4-55687 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Prabhakara, Prathik A1 - Mielentz, Frank A1 - Stolpe, Heiko A1 - Behrens, Matthias A1 - Lay, Vera A1 - Niederleithinger, Ernst T1 - Validation of novel ultrasonic phased array borehole probe by using simulation and measurement N2 - Low-frequency ultrasonic testing is a well-established non-destructive testing (NDT) method in civil engineering for material characterization and the localization of cracks, reinforcing bars and delamination. A novel ultrasonic borehole probe is developed for in situ quality assurance of sealing structures in radioactive waste repositories using existing research boreholes. The aim is to examine the sealing structures made of salt concrete for any possible cracks and delamination and to localize built-in components. A prototype has been developed using 12 individual horizontal dry point contact (DPC) shear wave transducers separated by equidistant transmitter/receiver arrays. The probe is equipped with a commercially available portable ultrasonic flaw detector used in the NDT civil engineering industry. To increase the sound pressure generated, the number of transducers in the novel probe is increased to 32 transducers. In addition, the timed excitation of each transducer directs a focused beam of sound to a specific angle and distance based on the previously calculated delay time. This narrows the sensitivity of test volume and improves the signal-to-noise ratio of the received signals. In this paper, the newly designed phased array borehole probe is validated by beam computation in the CIVA software and experimental investigations on a half-cylindrical test specimen to investigate the directional characteristics. In combination with geophysical reconstruction methods, it is expected that an optimised radiation pattern of the probe will improve the signal quality and thus increase the reliability of the imaging results. This is an important consideration for the construction of safe sealing structures for the safe disposal of radioactive or toxic waste. KW - Ultrasound KW - Phased array KW - Concrete KW - Borehole PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-565722 DO - https://doi.org/10.3390/s22249823 SN - 1424-8220 VL - 22 IS - 24 SP - 1 EP - 16 PB - MDPI CY - Basel AN - OPUS4-56572 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Epple, Niklas A1 - Niederleithinger, Ernst A1 - Fontoura Barroso, Daniel T1 - Coda Wave Interferometry for Monitoring Bridges with Embedded Ultrasonic Transducers – Lessons Learned at the Gänstorbrücke Bridge Ulm, Germany N2 - Ultrasonic Coda Wave interferometry has the potential to detect minute changes in scattering materials like concrete. By permanently installing ultrasonic transducers in concrete, DFG Research unit CoDA aims to develop methods for concrete damage assessment in Germany's aging infrastructure. To test the methods developed in simulations and laboratory experiments on a large scale, we have implemented several ultrasonic transducers at the Gänstorbrücke Ulm, one of Germany's most monitored road bridges. Since fall 2020 we are monitoring parts of the center of the Bridge, as well as an abutment, and compare the results to the commercial monitoring system. All data is recorded with a self-made data collection device, the so-called W-Box, and analyzed with different coda wave-based algorithms to detect signal and volumetric velocity changes. The long-term measurements show that the influence of temperature changes on strains and therefore ultrasound velocity changes calculated with coda waves can be monitored. The capabilities and limitations of the coda wave-based monitoring system are tested in a controlled experiment. Static loading using a truck with varying loads at several positions allows the calibration of the system to improve the detectability of possibly damaging loads and changes induced by this loading. A map of velocity change analyzing data from this load experiment shows that the influence of load on the material and strain distribution can be detected with array measurements. T2 - NDT-CE 2022 - The International Symposium on Nondestructive Testing in Civil Engineering CY - Zurich, Switzerland DA - 16.08.2022 KW - Coda Wave Interferometry KW - Ultrasound KW - Embedded sensors KW - Bridge Monitoring KW - Load Experiment PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-564531 SP - 1 EP - 8 AN - OPUS4-56453 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Epple, Niklas A1 - Niederleithinger, Ernst A1 - Fontoura Barroso, Daniel T1 - Coda Wave Interferometry for Monitoring Bridges with Embedded Ultrasonic Transducers – Lessons Learned at the Gänstorbrücke Bridge Ulm, Germany N2 - Ultrasonic Coda Wave interferometry has the potential to detect minute changes in scattering materials like concrete. By permanently installing ultrasonic transducers in concrete, DFG Research unit CoDA aims to develop methods for concrete damage assessment in Germany's aging infrastructure. To test the methods developed in simulations and laboratory experiments on a large scale, we have implemented several ultrasonic transducers at the Gänstorbrücke Ulm, one of Germany's most monitored road bridges. Since fall 2020 we are monitoring parts of the center of the Bridge, as well as an abutment, and compare the results to the commercial monitoring system. All data is recorded with a self-made data collection device, the so-called W-Box, and analyzed with different coda wave-based algorithms to detect signal and volumetric velocity changes. The long-term measurements show that the influence of temperature changes on strains and therefore ultrasound velocity changes calculated with coda waves can be monitored. The capabilities and limitations of the coda wave-based monitoring system are tested in a controlled experiment. Static loading using a truck with varying loads at several positions allows the calibration of the system to improve the detectability of possibly damaging loads and changes induced by this loading. A map of velocity change analyzing data from this load experiment shows that the influence of load on the material and strain distribution can be detected with array measurements. T2 - NDT-CE 2022 - The International Symposium on Nondestructive Testing in Civil Engineering CY - Zurich, Switzerland DA - 16.08.2022 KW - Coda Wave Interferometry KW - Ultrasound KW - Embedded sensors KW - Bridge Monitoring KW - Load Experiment PY - 2022 AN - OPUS4-56454 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rabe, U. A1 - Pudovikov, S. A1 - Herrmann, H.-G. A1 - Wiggenhauser, H. A1 - Prabhakara, Prathik A1 - Niederleithinger, Ernst T1 - Evaluation of retroreflective corner echo for detection of surface breaking cracks in concrete by ultrasound N2 - The retroreflective corner echo is used, for example, in ultrasonic non-destructive testing of metals to find fatigue cracks in tubes or shafts. If the much weaker crack tip signal is additionally detected, the crack length can also be determined. A corner reflection occurs in cases of surface breaking cracks with predominantly perpendicular orientation to the surface. The intensity of the corner reflection depends on the angle of incidence and on the ultrasonic wave mode used. For the reliable detection of vertical surface breaking cracks in metals, transversal waves are commonly used, which propagate at an angle of 37° to 53° to the inspection surface. As shown in this contribution, the wide spread low frequency ultrasonic arrays with dry point contact sources available for ultrasonic testing of concrete also allow to receive corner echoes. These devices generate transversal waves in concrete structures with a large divergence of the sound field. A series of experiments was carried out with such dry point contact arrays on concrete specimens with artificial test defects and controlled induced cracks of different depths. The ultrasonic time-of-flight signals were recorded, exported and reconstructed utilising the SAFT (Synthetic Aperture Focusing Technique) algorithm. The SAFT reconstruction parameters were adjusted to visualize the corner echo indication. As will be shown, with this targeted processing, the reproducible detection of surface breaking cracks in concrete is possible. The retroreflective corner echo can thus be exploited in civil engineering for non-destructive inspection of concrete. T2 - NDT-CE 2022 CY - Zurich, Switzerland DA - 16.08.2022 KW - Concrete KW - Crack depth KW - Ultrasound KW - SAFT PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-563365 UR - https://www.ndt.net/article/ndtce2022/paper/27256_manuscript.pdf IS - 27256 SP - 1 EP - 4 PB - NDT.net AN - OPUS4-56336 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Landis, E. A1 - Hassefras, Emiel A1 - Oesch, Tyler A1 - Niederleithinger, Ernst T1 - A Microstructural Basis for Diffuse Ultrasound in Concrete N2 - Attenuation of ultrasonic signals in concrete has the potential to carry much information about the microstructure of the material. In this work a series of concrete specimens of varying porosities and pore size distributions were internally imaged with x-ray computed tomography (CT), and then subsequently examined with throughtransmission ultrasound. The CT images were used to quantify both capillary porosity of cement paste as well as internal interfaces that are likely to produce elastic wave scattering. Ultrasound signals were represented as a diffusion process such that absorption and scattering attenuation could be isolated. As implemented, the diffusion model was a poor predictor of capillary porosity, while diffusivity was a reasonable predictor of scattering interfaces. Diffusivity was found to scale extremely well with small scale porosity, which made it a good predictor of compressive strength. T2 - NDT-CE 2022 CY - Zurich, Switzerland DA - 16.08.2022 KW - Concrete KW - X-ray tomography KW - Ultrasound PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-563371 UR - https://www.ndt.net/article/ndtce2022/paper/61592_manuscript.pdf SP - 1 EP - 4 PB - NDT.net AN - OPUS4-56337 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, T. A1 - Sens-Schönfelder, C. A1 - Epple, Niklas A1 - Niederleithinger, Ernst T1 - Imaging of Small-Scale Heterogeneity and Absorption Using Adjoint Envelope Tomography: Results From Laboratory Experiments N2 - To complement the information provided by deterministic seismic imaging at length scales above a certain resolution limit we present the first application of adjoint envelope tomography (AET) to experimental data. AET uses the full envelopes of seismic records including scattered coda waves to obtain information about the distribution of absorption and small-scale heterogeneity which provide complementary information about the investigated medium. Being below the resolution limit this small-scale structure cannot be resolved by conventional tomography but still affects wave propagation by attenuating ballistic waves and generating scattered waves. Using ultrasound data from embedded sensors in a meter-sized concrete specimen we image the distribution of absorption and heterogeneity expressed by the intrinsic quality factor Q−1 and the fluctuation strength ɛ that characterizes the strength of the heterogeneity. The forward problem is solved by modeling the 2-D multiple nonisotropic scattering in an acoustic medium with spatially variable heterogeneity and attenuation using the Monte-Carlo method. Gradients for the model updates are obtained by convolution with the back-propagated envelope misfit using the adjoint formalism in analogy to full waveform inversion. We use a late coda time window to invert for absorption and an earlier time window to infer the distribution of heterogeneity. The results successfully locate an area of salt oncrete with increased scattering and concentric anomalies of intrinsic attenuation. The resolution test shows that the recovered anomalies constitute reasonable representations of internal structure of the specimen. KW - Ultrasound KW - Scattering KW - Tomography KW - Concrete KW - Heterogeneity PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-563163 DO - https://doi.org/10.1029/2022JB024972 SN - 2169-9313 VL - 127 IS - 11 SP - 1 EP - 21 PB - American Geophysical Union AN - OPUS4-56316 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lay, Vera A1 - Effner, Ute A1 - Niederleithinger, Ernst A1 - Arendt, J. A1 - Hofmann, M. A1 - Kudla, W. T1 - Ultrasonic quality assurance at magnesia shotcrete sealing structures N2 - Engineered barriers are a key element to enable safe nuclear waste disposal. One method currently under research for their construction is magnesia concrete applied in a shotcrete procedure. In this study, the ultrasonic echo method is evaluated as a means for quality assurance. Imaging of internal structures (backwall, boreholes) and defects, such as delamination, has successfully been achieved in the shotcrete. Additionally, detailed information about the potential cause of selected reflectors are obtained by phase analysis. In several test blocks of various sizes, no consistent concrete section boundaries have been found by ultrasonic imaging, which was verified by subsequent drilling and complementary tests. An experiment with artificial defects imitating cracks, air-filled voids, and material with lower density has been challenging and shows the limitations of the current methods. Although significant defects, such as a large delamination, are reliably identified, several smaller defects are not identified. Generally, ultrasonic imaging provides a suitable base as a mean for quality assurance during and after the construction of sealing structures. However, further developments are required to enhance the reliability of the method and a full validation is still pending. Still, the method has potential to increase the safety of nuclear waste repositories. KW - Ultrasound KW - Imaging KW - Engineered barrier systems KW - Underground KW - Shotcrete PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-563170 DO - https://doi.org/10.3390/s22228717 SN - 1424-8220 VL - 22 IS - 22 SP - 1 EP - 16 PB - MDPI CY - Basel AN - OPUS4-56317 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Imani, A. A1 - Niederleithinger, Ernst A1 - Brown, M. C. T1 - Nondestructive Evaluation of Bridges without Structural Plans for Load Rating Purposes N2 - According to the NBI database, more than 21,000 in-service U.S. bridges lack sufficient structural documentation necessary for analytical load rating. Among these are a significant proportion of older prestressed concrete bridges. Given the lack of documentation on the reinforcing layout, such structures cannot be load rated analytically and are often subject to engineering judgement as the basis for rating. Otherwise, the typical approach for load rating such bridges is to conduct costly proof load testing and destructive probing together with making conservative assumptions. Therefore, any improvement to current practices will benefit DOTs and taxpayers alike. Accurately reconstructed 3D images of the girders to reflect the internal reinforcement could mitigate the need for costly, if not impractical, destructive testing and proof load testing, and help reduce dependency on conservative assumptions. This study examines a comprehensive NDE approach using ultrasonic tomography and GPR to aid in gathering structural information for load rating purposes. Different types of AASHTO and hollow core girders were tested. T2 - NDT-CE 2022 CY - Zurich, Switzerland DA - 16.08.2022 KW - Ultrasound KW - Radar KW - Bridges KW - Load rating PY - 2022 AN - OPUS4-56356 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schumacher, T. A1 - Niederleithinger, Ernst T1 - Combining Passive and Active Ultrasonic Stress Wave Monitoring Techniques: Opportunities for Condition Evaluation of Concrete Structures N2 - Concrete structures are invaluable assets to a society and managing them efficiently and effectively can be supported by information gathered through structural health monitoring (SHM). In this paper, a combined approach based on passive, i.e., acoustic emission (AE), and active, i.e., ultrasonic stress wave (USW) monitoring techniques for application to concrete structures is proposed and evaluated. While AE and USW are based on the same underlying physics, i.e., wave motion in solids, they differ fundamentally with respect to the nature of the source. For the former, external stimuli such as mechanical loads or temperature cause the rapid release of energy from initially unknown locations. As a result, AE events are unique and cannot be repeated. For the latter, a known source at a known location is employed at a specified time. This approach is thus controlled and repeatable. It is argued that a combination of these two techniques has the potential to provide a more comprehensive picture of ongoing fracture processes, damage progression, as well as slowly occurring aging and degradation mechanisms. This combined approach does thus promise new opportunities to support condition assessment of concrete structures. After providing an overview and comparison of the two techniques, results, and observations from a full-scale laboratory experiment and an in-service bridge monitoring study are discussed to demonstrate the promise of the proposed combined monitoring approach. Finally, suggestions for further work are presented. T2 - NDT-CE 2022 CY - Zurich, Switzerland DA - 16.08.2022 KW - Ultrasound KW - Acoustic emission KW - Concrete structures KW - Monitoring PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-563242 UR - https://www.ndt.net/article/ndtce2022/paper/61607_manuscript.pdf SP - 1 EP - 11 PB - NDT.net AN - OPUS4-56324 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zeipert, H. A1 - Claes, L. A1 - Johannesmann, S. A1 - Lugovtsova, Yevgeniya A1 - Nicolai, Marcel A1 - Prager, Jens A1 - Henning, Bernd ED - Jumar, U. T1 - An approach to adhesive bond characterisation using guided acoustic waves in multi-layered plates N2 - An approach for the non-destructive characterisation of adhesive bonds using guided ultrasonic waves is presented. Pulsed laser radiation is used to thermoacoustically excite broadband ultrasonic waves in a multi-layered sample, consisting of a metal plate adhesively joined to a polymeric layer using synthetic resin. The resulting signals are received by a purpose-built piezoelectric transducer. Varying the distance between excitation and detection yields spatio-temporal measurement data, from which the dispersive properties of the propagating waves can be inferred using a two-dimensional Fourier transform, assuming the plates to act as coupled waveguides. Coupled multi-layered waveguides show an effect referred to as mode repulsion, where the distance between certain modes in the frequency-wavenumber domain is assumed to be a measure of coupling strength. Measurements at different stages of curing of the adhesive layer are performed and evaluated. A comparison of the results shows changes in the dispersive properties, namely an increased modal bandwidth for the fully cured sample as well as an increased modal distance. KW - Adhesive bonding KW - Guided waves KW - Non-destructive testing KW - Ultrasound PY - 2021 DO - https://doi.org/10.1515/auto-2021-0089 VL - 69 IS - 11 SP - 962 EP - 969 PB - De Gruyter CY - Berlin/Boston AN - OPUS4-53762 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lay, Vera A1 - Baensch, Franziska A1 - Johann, Sergej A1 - Sturm, Patrick A1 - Mielentz, Frank A1 - Prabhakara, Prathik A1 - Hofmann, Detlef A1 - Niederleithinger, Ernst A1 - Kühne, Hans-Carsten T1 - SealWasteSafe: materials technology, monitoring techniques, and quality assurance for safe sealing structures in underground repositories N2 - Within the project SealWasteSafe, we advance construction materials and monitoring concepts of sealing structures applied for underground disposal of nuclear or toxic waste. As these engineered barriers have high demands concerning integrity, an innovative alkali-activated material (AAM) is improved and tested on various laboratory scales. This AAM has low reaction kinetics related to a preferential slow release of the heat of reaction in comparison to alternative salt concretes based on Portland cement or magnesium oxychloride cements. Hence, crack formation due to thermally induced strain is reduced. After successful laboratory scale analysis (Sturm et al., 2021), the AAM is characterised on a larger scale by manufacturing test specimens (100–300 L). Conventional salt concrete (DBE, 2004) and the newly developed AAM are compared using two specimen geometries, i.e. cylindrical and cuboid. A comprehensive multisensor monitoring scheme is developed to compare the setting process of AAM and salt concrete for these manufactured specimens. The analysed parameters include temperature and humidity of the material, acoustic emissions, and strain variations. Passive sensor systems based on radiofrequency identification technology (RFID) embedded in the concrete, enable wireless access to temperature and humidity measurements and are compared to conventional cabled systems. Additionally, fibre-optic sensors (FOS) are embedded to record strain, but also have potential to record temperature and moisture conditions. Part of this project aims at demonstrating the high reliability of sensors and also their resistance to highly alkaline environments and to water intrusion along cables or at sensor locations. Further technical improvements were implemented so that first results clearly show the scalability of the setting process from previous small-scale AAM experiments and particularly the high potential of the newly developed approaches. Furthermore, ultrasonic methods are used for quality assurance to detect obstacles, potential cracks and delamination. On the one hand, both active and passive ultrasonic measurements complement the results obtained from the multisensor monitoring scheme for the produced specimens. On the other hand, the unique large aperture ultrasonic system (LAUS) provides great depth penetration (up to nearly 10 m) and can thus be applied at in situ sealing structures built as a test site in Morsleben by the Federal Company for Radioactive Waste Disposal (Bundesgesellschaft für Endlagerung, BGE) as shown by Effner et al. (2021). An optimised field lay-out identified from forward modelling studies and advanced imaging techniques applied to the measured data will further improve the obtained results. To characterise the inside of the test engineered barrier and achieve a proof-of-concept, an ultrasonic borehole probe is developed to enable phased arrays that can further improve the detection of potential cracks. Modelling results and first analysis of semispherical specimens confirmed the reliability of the directional response caused by the phased arrays of the newly constructed ultrasonic borehole probe. Overall, the project SealWasteSafe improves the construction material, multisensor monitoring concepts and ultrasonics for quality assurance. This will help to develop safe sealing structures for nuclear waste disposal. The outcomes are particularly valuable for salt as a host rock but partly also transferrable to alternative conditions. T2 - Safe ND Interdisciplinary research symposium on the safety of nuclear disposal practices CY - Berlin, Germany DA - 10.11.2021 KW - Borehole probe KW - SealWasteSafe KW - Engineered barrier KW - Materials technology KW - Monitoring KW - AAM KW - Ultrasound PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-539172 DO - https://doi.org/10.5194/sand-1-127-2021 VL - 1 SP - 127 EP - 128 PB - Copernicus AN - OPUS4-53917 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Lay, Vera A1 - Baensch, Franziska A1 - Johann, Sergej A1 - Sturm, Patrick A1 - Mielentz, Frank A1 - Prabhakara, Prathik A1 - Hofmann, Detlef A1 - Niederleithinger, Ernst A1 - Kühne, Hans-Carsten T1 - SealWasteSafe: materials technology, monitoring techniques, and quality assurance for safe sealing structures in underground repositories N2 - Within the project SealWasteSafe, we advance construction materials and monitoring concepts of sealing structures applied for underground disposal of nuclear or toxic waste. As these engineered barriers have high demands concerning integrity, an innovative alkali-activated material (AAM) is improved and tested on various laboratory scales. This AAM has low reaction kinetics related to a preferential slow release of the heat of reaction in comparison to alternative salt concretes based on Portland cement or magnesium oxychloride cements. Hence, crack formation due to thermally induced strain is reduced. After successful laboratory scale analysis (Sturm et al., 2021), the AAM is characterised on a larger scale by manufacturing test specimens (100–300 L). Conventional salt concrete (DBE, 2004) and the newly developed AAM are compared using two specimen geometries, i.e. cylindrical and cuboid. A comprehensive multisensor monitoring scheme is developed to compare the setting process of AAM and salt concrete for these manufactured specimens. The analysed parameters include temperature and humidity of the material, acoustic emissions, and strain variations. Passive sensor systems based on radiofrequency identification technology (RFID) embedded in the concrete, enable wireless access to temperature and humidity measurements and are compared to conventional cabled systems. Additionally, fibre-optic sensors (FOS) are embedded to record strain, but also have potential to record temperature and moisture conditions. Part of this project aims at demonstrating the high reliability of sensors and also their resistance to highly alkaline environments and to water intrusion along cables or at sensor locations. Further technical improvements were implemented so that first results clearly show the scalability of the setting process from previous small-scale AAM experiments and particularly the high potential of the newly developed approaches. Furthermore, ultrasonic methods are used for quality assurance to detect obstacles, potential cracks and delamination. On the one hand, both active and passive ultrasonic measurements complement the results obtained from the multisensor monitoring scheme for the produced specimens. On the other hand, the unique large aperture ultrasonic system (LAUS) provides great depth penetration (up to nearly 10 m) and can thus be applied at in situ sealing structures built as a test site in Morsleben by the Federal Company for Radioactive Waste Disposal (Bundesgesellschaft für Endlagerung, BGE) as shown by Effner et al. (2021). An optimised field lay-out identified from forward modelling studies and advanced imaging techniques applied to the measured data will further improve the obtained results. To characterise the inside of the test engineered barrier and achieve a proof-of-concept, an ultrasonic borehole probe is developed to enable phased arrays that can further improve the detection of potential cracks. Modelling results and first analysis of semispherical specimens confirmed the reliability of the directional response caused by the phased arrays of the newly constructed ultrasonic borehole probe. Overall, the project SealWasteSafe improves the construction material, multisensor monitoring concepts and ultrasonics for quality assurance. This will help to develop safe sealing structures for nuclear waste disposal. The outcomes are particularly valuable for salt as a host rock but partly also transferrable to alternative conditions. T2 - Safe ND Interdisciplinary research symposium on the safety of nuclear disposal practices CY - Berlin, Germany DA - 10.11.2021 KW - Borehole probe KW - SealWasteSafe KW - Engineered barrier KW - Materials technology KW - AAM KW - Monitoring KW - Ultrasound PY - 2021 AN - OPUS4-53919 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Büttner, C. A1 - Niederleithinger, Ernst A1 - Buske, S. A1 - Friedrich, C. T1 - Ultrasonic Echo Localization Using Seismic Migration Techniques in Engineered Barriers for NuclearWaste Storage N2 - In the framework of non-destructive-testing advanced seismic imaging techniques have been applied to ultrasonic echo data in order to examine the integrity of an engineered test-barrier designed to be used for sealing an underground nuclear waste disposal site. Synthetic data as well as real multi-receiver ultrasonic data acquired at the test site were processed and imaged using Kirchhoff prestack depth migration reverse time migration (RTM). In general, both methods provide a good Image quality as demonstrated by various case studies, however deeper parts within the test barrier containing inclined reflectors were reconstructed more accurately by RTM. In particular, the image quality of a specific target reflector at a depth of 8 m in the test-barrier has been significantly improved compared to previous investigations using synthetic aperture Focusing technique, which justifies the considerable computing time of this method. KW - Radioactive waste disposal KW - Engineered barrier KW - Ultrasound KW - Imaging KW - Crack detection PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-537956 DO - https://doi.org/10.1007/s10921-021-00824-3 SN - 0195-9298 VL - 40 IS - 4 SP - 1 EP - 10 PB - Springer AN - OPUS4-53795 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Niederleithinger, Ernst A1 - Wang, Xin A1 - Epple, Niklas A1 - Schumacher, T. A1 - Ahmend, S. A1 - Klikowicz, P. T1 - Ultrasonic coda wave monitoring of concrete structures: First experiences with large-scale experiments and real structures N2 - Ultrasonic monitoring, making use of the sensitivity of the coda of repeated transmission meas-urements to changes in stress, temperature, moisture, as well as localized or distributed damage, has gotten at-tention in structural health monitoring (SHM) research recently. Analysis methods such as coda wave inter-ferometry (CWI), including its nonlinear extension, have been shown to be able to measure ultrasonic wave velocity changes with a 1∙10-5 resolution, while indicators such as cross-correlation or cross-coherence have been used to distinguish between reversible and irreversible changes. Several small- and large-scale laboratory experiments have demonstrated that stress changes in structures can be captured or damage detected in a very early stage. The use of this technique for pre-warning before failure are currently under investigation, as well as detailed research on the physical causes and the connection between ultrasonic wave properties and materi-al/structural behavior. Recently, several of large-scale laboratory and real structures have been instrumented with embedded ultrasonic transducers to gather experience and evidence on how to use this technology in re-al-world applications. Preliminary results from installations on a new bridge, an existing bridge, a tunnel, a la-boratory earthquake test as well as a historic stadium in Germany, Poland, and the United States, respectively, are presented. Environmental influences (mainly temperature) and validation by load tests are discussed. T2 - IABMAS 2020 CY - Online meeting DA - 11.04.2021 KW - Ultrasound KW - Monitoring KW - Coda wave interferometry KW - Concrete KW - Bridges PY - 2021 AN - OPUS4-54167 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Niederleithinger, Ernst A1 - Wang, Xin A1 - Epple, Niklas A1 - Schumacher, T. A1 - Ahmend, S. A1 - Klikowicz, P. ED - Yokota, H. ED - Frangopol, D. W. T1 - Ultrasonic coda wave monitoring of concrete structures: First experiences with large-scale experiments and real structures N2 - Ultrasonic monitoring, making use of the sensitivity of the coda of repeated transmission meas-urements to changes in stress, temperature, moisture, as well as localized or distributed damage, has gotten at-tention in structural health monitoring (SHM) research recently. Analysis methods such as coda wave inter-ferometry (CWI), including its nonlinear extension, have been shown to be able to measure ultrasonic wave velocity changes with a 1∙10-5 resolution, while indicators such as cross-correlation or cross-coherence have been used to distinguish between reversible and irreversible changes. Several small- and large-scale laboratory experiments have demonstrated that stress changes in structures can be captured or damage detected in a very early stage. The use of this technique for pre-warning before failure are currently under investigation, as well as detailed research on the physical causes and the connection between ultrasonic wave properties and materi-al/structural behavior. Recently, several of large-scale laboratory and real structures have been instrumented with embedded ultrasonic transducers to gather experience and evidence on how to use this technology in re-al-world applications. Preliminary results from installations on a new bridge, an existing bridge, a tunnel, a la-boratory earthquake test as well as a historic stadium in Germany, Poland, and the United States, respectively, are presented. Environmental influences (mainly temperature) and validation by load tests are discussed. KW - Coda wave interferometry KW - Structural health monitoring KW - Ultrasound KW - Concrete KW - Bridges PY - 2021 SN - 978-0-367-23278-8 DO - https://doi.org/10.1201/9780429279119-345 SP - 2525 EP - 2531 PB - Taylor & Francis CY - London, UK AN - OPUS4-54168 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Niederleithinger, Ernst T1 - NDT CE from simple detectors to deep insight and quantitative structural assessment N2 - Non-destructive testing methods are available in civil engineering for decades to estimate concrete properties or to detect flaws and features. But recently we have seen the dawn of next-generation tools, methods, and applications. Some of them will be discussed in the web talk: – Better tools: deeper and more detailed insight into concrete constructions – Better methods: Quantitative use in probabilistic structural assessment – Better rules: Towards standardization, qualification, and certification – Better application: Digitalization and Elimination of the boundaries between NDT, SHM, and BIM: NDT-CE 4.0 Not enough? I might show, how cosmic rays might become a game-changer in NDT-CE. This live webinar record was provided by https://eurostruct.org T2 - Eurostruct Live Talk CY - Online meeting DA - 12.05.2021 KW - NDT-CE KW - Concrete KW - Ultrasound KW - Muons PY - 2021 AN - OPUS4-54158 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Niederleithinger, Ernst A1 - Sodeikat, C. A1 - Epple, Niklas A1 - Liao, Chun-Man A1 - Hindersmann, I. T1 - Acoustic emission and ultrasonic monitoring of a prestressed concrete bridge in its final years N2 - Many European bridges built in the 1950s, 60s and 70s must be re-placed in the next decade due to structural deficiencies, insufficient load capacity or other issues. However, the existing bridges must be used for another couple of years even if flaws and damages already have been detected. In Germany, several prestressed concrete bridges have been instrumented with acoustic emission detection systems to detect wire breaks and to provide early warning signs before failure. To evaluate and interpret the consequences of wire breaks additional instrumentation and accompanying measures as finite element modeling are required. At a bridge in southern Germany we have complemented such a system with active ultrasonic monitoring. Repeated ultrasonic measurements are evaluated with a very sensible algorithm called coda wave interferometry. This method, inspired by seismology, has been shown to deliver early warning signs in lab experiments. Large volumes of concrete can be monitored with a limited network of ultrasonic transducers. We will report on the installation, capabilities, and lim-itations as well as first results. T2 - 1st Conference of the European Association on Quality Control of Bridges and Structures (Eurostruct) CY - Padua, Italy DA - 29.08.2021 KW - Bridge KW - Concrete KW - Acoustic emission KW - Ultrasound KW - Monitoring PY - 2021 AN - OPUS4-54160 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -